Measuring instrument



Nov. 13, 1928- 1,691,342

. I R. D. EVANS umsunme ms'rnuuam Filed July 31, 1924 INVENTOR fioberf 0 5141/76.

I ATTORNEY Patented Nov. 13, 1 928.

UNITED [STATES I 1,691,342 PATENT FFICE."

ROBERT DQ EVANS; OF WI LKINSBURG, PEHNSYLVALHA; .ASSIGISTOE TO I ESTINGHOUSE ELECTRIC & MANUFACTURING COMPillllY, A CORPS.

" i MEASURING INSTRQ'MENT.

7 Application filed. July 21,

of a polyphase quantity,suchas current or voltage' I V Another object of myinvcntion is to proride :1 switch, on electrical network and an indicating instrument so connected to the conductors of a polyphase circuit that upon opera ing the switch, either thepositive or the 1185 *ive sequence component of polyphase iiriitity may he measured, as desired.

' i In practicing my'invention, I provide tire. and the no:

means such as a static network siuiiliir to thot disclosed in my prior Patcnt No, 1,53 ,581 dated April 28, 1925, for segregating the posi: J itiite sequence components or". cnrrent, volta e, or power in a. polyphase circuit, I also provide a. meter and a switch in terpos'ed'hetwecn this meter and toe static network in such a manner that by actuating the switch in one direction or the other, the

circuit connections of the meter are so reversed that it measures either the positive or the negative component.

Referring to the accompanying drawings,

, wherein several embodiments of my inven- 'tion;

cont

tion are shown to facilitate a clearer understa ding thereof,

Figure 1 is a diagrammatic view of one torn of an instrument constru'cted in accordnncowith my nvention I ,is a similar view of a modification,

int-2 and Fig. Sis a similar vicw o'f another modificatransformer" and 5. A

responsivedevice 9, such asan 311*11110t61,13bifltl et across the resistors and thoreactor in series The I Serial n'srzseea.

currentthrough the resistor (3 is substantially in ph with the applied voli'ag ivliereas rough the resistor 7 and the rc-. c the appliedvoltage 60. ii rotary switch 10, comprising fixed segoll. and 1:2 and movable segmentsl-B. is posed lzetween the transformers 4t and 5 he network con'lprising the resistors 6 I e reactor 8, With the switch on s (wn, and the proper phasee ainzrnoer 9 is act-sated in acith the positivesequence or direct tor 8 l 1 of current in the cirat1n. the switch 10 t0 the i opposite position, the connece i 1; and' the static network to i isfc-rmers and 5 are reversed, is actuated in. accordance with .t of current, assun'iing that the cur rents o inlslanccd.

i l he understood that the positive sequence component is a measure of the load on th and the negative sequence com- 1 t :1 measure of the degree of unhaL once or" the hasesof the circuit.

- The fixed. segu'ients 11 serve to short-circuit the current transt ormers l, and 5 while the switch is being actuated from one position to the othe... This provision is necessary to prevent inii'zring the current transformers due to the h h voltage produced when they are opencircuited.

In Fig. 2 is shown :11 similar arrangement for measuring either the positive or'the negative sequence component of voltage. Ohvionsly, a similar arrangement will provide for 'measur the symmetrical components of power. 1' mine the principles set forth in i prior application referred to above.

in 2, voltage transformers 14 and 15 are connected across t 1e conductors 1, 2 and 3 of the circuit. A st .tic network comprising resistors 6 and 7 and a reactor 8 is associated with a voi'tage-responsive device 16. The cur ent through the resistor 7 and reactor 8 the phase voltage A switch 10 is interposed between the potential transformers 1 nd 15 the static network. The opera,- 0 tch i0 reverses the connections of: the s eitl'ier the positive or the negative seico com onent of voltage as desired.

o v 1 l u 7 is snown a modified form of cureta onal or negative sequence.

-21 o? the potential tr ms-formers 14 and 15 so 1.] i

rent-responsive instrument. Two current transformers 4t and 5 are associated with the conductors 2 and 3 of a polyphase circuit. The static network comprising resistors 6 and 7 and a reactor 8 is connected in a bridge relation to the current-responsive device 9 and the balancing impedance 17. A switch 10 is provided, as before, to reverse the connections of the current transformers 4 and 5 to the static network. In actual practice, an arrange nent similar to that shown in Figure 1 would he provided to prevent open-circuiting the transformers 4 and 5 but this is omitted fron jthe drawing for the sake of simplicity. Vith the'switch 10 in the position shown, the annneter 9 is actuated in accordance with the positive or the negative sequence component of "current depending upon the phase sequence of the circuit. VVhenthe switch 10 is thrown to the other position, the ammeter 9 is actuated in accordance with the other component. The instrument 9 may be any current-responsive device, such as a relay or 'a measuring instrument,

It will be apparent that I have devised an instrun'ient by which either one of the two symmetrical components of an unbalanced polyphase system may be obtained atwill by throwing a switch. The utility of such a device will be apparent. I do not consider that ing short-circuiting segments, for actuating said device in accordance with either component, as desired.

2. An instrument comprisin an electroresponsive device, means including a current transformer associated with said device for segregating the positive and negative sym metrical components of an electrical quantity, and means, including a switch, for actuating said device in accordance with either the positive or negative sequence component, I

as desired, said switch having means en1- bodied therein for short circuiting said current transformer during an operation of said switch.

In testimony whereof, I have hereunto subscribed my name this 29th day of July 1924.

ROBERT D. EVANS. 

